Climate Controls Why does temperature vary so much in the world? The answer: PSALMON

1)Prevailing Winds: High pressure (think of a bulldozer pushing down the air)-keeps air close to the ground it does not rise-therefore dry conditions Low pressure the air rises, as it rises it cools, condenses (clouds), and precipitation happens. At 0 degrees-Low Pressure 30 degrees-High Pressure 60 – Low Pressure 90-High pressure

2) Slope of the Land Direction a slope faces In the northern hemisphere: south facing slopes are drier (more sunshine) north facing slopes are wetter and have less sun

3) Altitude: the higher you go up, the colder it gets. Why? Less dust, greenhouse gases, water vapour, etc. to trap heat coming up from the earth's surface. As elevation increases – temperature decreases (think of going up a mountain)—1 degrees for every 150 meters of elevation. Air becomes thinner cannot conserve (keep) heat  that is why pressure decreases with elevation.

4) Latitude: the further north you go in the northern hemisphere, the colder it gets. Why? a) Curvature of the earth: the sun strikes the earth in a very concentrated fashion at the equator, whereas at the poles, the sun's rays are much more spread out. b) The Seasons: spring, summer, fall, and winter result in different amounts of heat coming to the earth. This is caused by the changing position of where the sun is directly overhead on the earth's surface during the year and the tilt of the earth's axis. i.e. Mar. 21 (Vernal Equinox) and Sept. 21 (Autumnal Equinox): the sun is directly overhead at the equator. Dec. 21 (Winter Solstice): the sun is directly overhead at the Tropic of Capricorn (23.5 S). June 21 (Summer Solstice): the sun is directly overhead at the Tropic of Cancer (23.5 N). Lower latitudes receive more sunlight – warm climates with small temperature ranges Higher latitudes = rays of sun are more spread out= colder climates more temperature extremes = evident in poles.

4) Mountain Barriers: stop the movement of cold air masses. This is due to the fact that cold air is dense and generally stays near to the ground. Air is forced to rise on the windward side of mountain causing precipitation Leeward side the wind falls creating clear, dry conditions=rain shadow eg Vancouver is shielded from most Arctic air masses by the Rockies and Coast Mountains. Mountains can also result in warm winds descending down slope eg a chinook: a warm wind. This westerly wind is dry and blows down the eastern side of the Rockies affecting cities such as Calgary.

5. Ocean Currents: can either warm or cool a coastal area by approximately two degrees Celsius. Warm and cold ocean currents circulate through out the world’s oceans and these have a heating/colling effect Gulf Stream (warm current) warms areas in Europe (Britain) making the climate moderate Cold Ocean Currents will create dry regions around the globe=Atacama desert in Chile is a result of cold ocean currents as the bring dry air from the see over land Note: Winds produce currents.

6) Nearness to Water or Continentality: the closer a city is to a large body of water, the more moderate will be its temperatures (i.e. maritime climate), whereas the further away a city is from the water, the greater the temperature extremes (i.e. continental climate). Locations near water=wetter/moderate Interior (Continental) locations are drier and have more temperature extremes Ex. Gobi Desert in Mongolia/China (dry interior conditions) Try to think of differences in climate between a place like Vancouver and Winnipeg…